Separators of the above-mentioned type are described in international patent applications WO 2009/033 514 A1 and WO 2009/003 627 A1. Nonwovens with a particle filling are described there, which are used as separators in batteries and energy storage devices.
Within the scope of the growing scarcity of natural resources and the associated costs increases for energy, energy storage devices—especially electric energy storage devices—are becoming more and more important for modern industrialized nations.
For the most part, capacitors and batteries are used as energy storage devices. At the present time, lithium-ion batteries are considered to be particularly promising. These batteries are already being used for mobile applications such as, for example, mobile telephones, camcorders, etc.
When these technologies are transferred to large-volume batteries, which are needed to store large amounts of electric energy, however, scale-up problems occur. A crucial problem here is the warming up and overheating of a battery. In the case of large batteries, the heat generated during charging and discharging processes does not dissipate very well, so that the individual components of the battery are exposed to a high thermal load that has the effect of shortening the service life of the battery. Therefore, higher requirements are made of the reliability, stability and service life of the individual components of a battery in order to avoid an internal short circuit or an explosion of the battery.
In order to ensure the economical use of lithium-ion batteries, in addition to enlarging the batteries, there is also a need to further increase their energy density or power density. In order to meet these requirements, new electrode materials are being developed for the anode as well as for the cathode.
For the cathode, high-voltage cathode materials are used that allow a higher cell voltage in the battery and thus also a higher capacity. The high-voltage cathode materials, especially when the battery is in the charged state, are strongly oxidizing materials that make totally new requirements of the components employed in a battery. On the anode side, the separator is in direct contact with strongly reducing electrode materials.
This gives rise to new requirements for the electrolytes and also for the separator, which is in direct physical contact with the electrodes.